Alkylation of isoparaffinic hydrocarbons



Patented Apr. 23, 1946 ALKYLA'noN or rsoraaarr'rmc nrnnoosanons Carl B. Linn, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application December 29, 1941,

Serial No. 4,784

I 13 Glaims.

This inventionrelates to the treatment of isoparafilnic hydrocarbons, both gaseous and liquid, to produce therefrom branchedchain parafilnic hydrocarbons of higher molecular weight. In a more specific sense this invention is concerned with a novel process for alkylating isoparaflinic hydrocarbons, comprising isobutane and relatively low-boiling normally liquid isoparafilns with normally gaseous or liquid olefins to produce normally liquid saturated hydrocarbons which may be utilized as components of gasoline suitable for use in airplane and automobile engines,

These isoparafflnic and olefinic hydrocarbons have been utilized in alkylation reactions in the presence of hydrogen fluoride alone or of hydrogen fluoride diluted by relatively small quantities of water. The present type of catalyst is a marked improvement over previous catalysts containing hydrogen fluoride in that the activity of the catalytic material may be controlled more accuratelyt by proper dilution with substances which are relatively inert catalytically-but which have substantial solubilities in liquid hydrogen v fiuori'de.' v V In one specific embodiment the present invention'comprises a process for synthesizing substantially saturated hydrocarbons of gasoline boiling range by alklating isoparamnic hydrocarbons with olefinic hydrocarbons in the presence of a catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion of a substantially non-oxidizing acid, ester, or anhydride of said acid.

A feature of the present invention is the addition to substantially anhydrous hydrogen fluoride of anon-aqueous diluent so that the ordinarily Substantially non-oxidizing vigorous reaction of anhydrous hydrogen fluoride on catalytic condensation reactions among hydrocarbons is moderated to the extent that reactions of alkylation occur in preference to other less desirable reactions. Alkylation is essentially a complex reaction since the simple union of isoparaffinlc and olefinic molecules to give the so-called primary reaction product is accompanied by many side reactions, among which are decomposition or cracking reactions and isomerization, which can, under certain conditions, change a substantial proportion of the primary product saturated hydrocarbon product is formed which boils within the boiling range of gasoline.

According to the process of the present invention, isoparafllns are contacted with olefins in the presence of a catalyst consisting of a major proportion by weight of liquid hydrogen fluoride and.

a relatively minor proportion by weight of a diluent or spacing agent selected from the aforementioned group of substantially non-oxidizirg compounds comprising organic acids, acids of phosphorus, hydroxyfluoboric acids, and also. anhydrides and esters of said acids. 7

'The organic acids comprise particularly the aliphatic monocarboxylic acids as formic, acetic, propionic, higher aliphatic monocarboxylic acids, and also hydrogen cyanide. Under the conditions of the process, these acids sometimes react with olefinsproducing thealkylesters of these acids which are also utilizable in the present process although not necessarily under the same conditions of operation or with equivalent results. inorganic acids utilizable in the present process include acids of phosphorus, such as phosphorous, ortho-phos- I fiuoboric acid which is obtainable by treating boric oxide with hydrogen fluoride, boric acid .withboron trifluoride, or a mixture of calcium fluoride and boric oxide with sulfuric acid.

Fluoro alkanes and fiuorochloro alkanes are also sometimes utilizable as diluents for hvdrogen fluoride alkylation catalysts under modified conditions of operation.

such as iso-octanes into a mixture of lower and higher boiling hydrocarbons frequently of lower antiknock value. Accordingly, the'present invention deals with the modification of hydrogen fluoride alkylation catalyst by the addition thereto'of certain substantially non-oxidizing acids, esters. or acid anhydrides, which moderate the Isobutane is the isoparafiin commonly subjected to alkylation although higher molecular weight isoparaflins also react with olefins under similar or modified conditions of operations to produce branched chain parafiins of higher boiling point than the isoparafflns'charged to the process. However, as the higher molecular weight isoparamnssuch' as isopentane, isohe'xane, etc.,

are themselves valuable constituentsof gasoline, I

they are consequently used less commonly as charging stocks for the alkylation process than is isobutane. Mono-olefins and particularly those containing from 3 to about 16 carbon atoms per molecule are utilizabie for alkylating isoparafllns bons but are separable from the alkylation products by distillation. Thus propane and normal butanemay be removed from the alkylatlon product while an isoparaflln such as isobutane, which is also separated from the reaction product, is recycled to further alkylation treatment.

In order to favor the alkylatlon reaction rather than olefin polymerization, the hydrocarbon charging stock includingthe isoparaffln and added olefin-containing fraction may be commingled with recycled isoparaflin so that the ratio of isoparaflin to olefin in the total hydrocarbon mixture charged to th alkylation zone is approximately 5:1. Insome cases this ratio may be as low as about 2:1 or as high as 10:1, or more, the exact ratio being somewhat dependent upon the particular isoparaflln and olefin or olefin-containing mixture charged.

The amount of hydrogen fluoride-containing catalyst employed is preferably from about 10 to about 100 parts by weight of catalyst per 100 parts by weight of hydrocarbons undergoing treatment at any one time, although in some operations other ratios of catalyst to hydrocarbons may be used. The concentrations of hydrogen fluoride in the composite catalysts which I have found desirable are limited by the solubilities in liquid hydrogen fluoride of the compounds chosenas catalyst diluents or spacing agents. Depending upon the reactivity of the hydrocarbon components in a given alkylation reaction, hydrogen fluoride of different concentrations and different proportions of hydrogen fluoride and diluents may be emplayed to form active alkylating catalysts.

Alkylation reaction temperatures between about 0 and about 50 C. are preferred, although satisfactory results may be obtained attemperatures as low as about --30 and as high as about +100 C. when reacting isoparafllns with olefins in the presence of a mixture'of hydrogen fluoride and a .diluent or spacing agent as herein described. As additional means of regulation of the upper limits of temperature, the proportions of hydrogen fluoride and diluent may be varied employed as diluting or spacing materials for hydrogen fluoride, it will be evident that a large number of catalyst composites of varying compositions may be made according to theneedsof different alkylation reactions. However, the different diluents or spacing agents are not necessarily equivalent in their action.

While in most cases the activity of the alkylat ing composite employed is due principally to the hydrogen fluoride, it is recognized that the compounds added thereto may at times exert a dellnite chemical influence upon'the reactions other than merely moderating the effect of the hydrogen fluoride; It is also evident that the selection of any particular diluent or mixture of diluents for use with hydrogen fluoride is determined largely by solubility relations, the ease of, alkylating the isoparafiinie hydrocarbons involved, the

general operating conditions, and the matter of.

economy in the cost of the reagents.

The process of the present invention is carried out in either batch or continuous types of operation. In a simple batch type process, an isoparaflln to be alkylated such as isobutane, is brought to the alkylating temperature within the approximate range specified and in the presence of the necessary amount of catalyst mixture and alkylation is effected by the gradual introduction of an olefin, or preferably of an olefin-isoparaflin mixture, under the surface of the liquid which is stirred mechanically to effect intimate contact between the catalyst and the reacting hydrocarbons and to prevent settling of the catalyst which is heavier than the liquid hydrocarbon mixture.

Alkylation may be allowed to progress to din'erent stages of reaction. In the case of the alkylation of isobutane by propene or butenes, good products from the standpoint of high antiknock gasoline are produced usually by maintainingat all times in the, reaction zone a molar excess of isoparaflin to olefin. The presence of such an excess of isoparaflins, generally at least 2 molecular proportions of isoparaflln per molecular proportion of olefin, tends to minimize undesirable polymerization reactions. The mixture of alkylation products and catalyst composite is removed perito produce good results provided they are coordinated properly with the reaction temperature and rate of charge of the isoparailln and olefin hydrocarbons. For instance, the reaction of isobutane with propene may require more severe conditions such as a somewhat higher temperature or a. catalyst containing a higher proportion of hydrogen fluoride to diluent than that used" for catalyzing the reaction of isobutane with the more reactive isobutene. superatmospheric prescdically from the batch type process and separated into a hydrocarbon layer and a catalyst layer, the latter being returned'to the reaction zone for further use while the hydrocarbon layer is fractionally distilled to separate therefrom the gasoline fraction and the excess of the isoparaflln originally charged to the process. The excess isoparafiln may be reacted further with an olefin in a subsequent alkylation treatment in the alkylation zone of the process.

It is usually preferable to carry out the alkylation reaction on a continuous basis by withdrawing from the alkylation reactor 9. complex mixture of excess unreacted isoparaflins and admixed normal paraflins, an alkylate of gasoline boiling range, higher boiling hydrocarbons, and catalyst at substantially the same rate as that at which sure, generally not in excess of about 20 atmos- V pheres, is employed to assist the reaction and to the hydrocarbons and catalyst in substantially composite, said complex mixture being withdrawn the v fresh and recycled hydrocarbon charging stock and mixture of fresh and recycled catalyst are-supplied to the alkylation reactor. In order 'to keep low the competing olefin polymerization reaction, the molar ratio of isoparaflins to olefina liquid state or to effect liquefaction of a portion of the reaction mixture.

From the statements hereinbefore set forth concerning the types of compounds which may be in the alkylating zone is kept high throughout the entire reaction. The ratio of isoparamn to olefin is subject-to some variation and is affected considerably by the method of introducing the olefincontaining fraction and by the efficiency of mixing. As the process is usually operated,

sumcient pressure is maintained upon the reaction mixture to keep a substantial proportion thereof in liquid state. The exact pressure necessary depends both upon the composition of the reaction mixture and the temperature employed. The alkylation reactor used in the process consists quite often of a coil or tower provided with baifles, orifice plates, or other mixing devices, or a vessel provided with a stirrer or other mechanical means otagitation although any method may be employed which satisfactorily effects intimate contact of the reacting hydrocarbons and mixture of catalyst and spacing agent employed.

The following examples are given to indicate results obtainable by the use of the present process, although it is not intended to limit the scope run to which additional quantities of isobutane and normal butene are introduced.

The foregoing specification and examples indicate the character of the process of the present invention and the nature of the results obtainable, although neither section is introduced with the idea of unduly limiting the generally broad scope of the invention.

I claim as my invention:

1. An alkylation process which comprises reacting an isoparaflin with an olefin in the presence of a liquid hydrogen fluoride catalyst to which has been added a minor proportion of a substantially non-oxidizing compound selected of the invention in exact correspondence with the examples.

Example I A mixture of 135 parts by weight ofv substan- I tially anhydrous hydrogen fluoride and 15 parts by weight of dihydroxyfluoboric acid having a boiling point of about 160 C. is placed in an autoclave of approximately 2000 volumes capacity equipped with a pressure-sealed stirring device. The autoclave is maintained at approximately 50 C. while 1000 volumes of a liquid mixture contaming 2 molecular proportions of isbutane and 1 molecular proportion of normal butene is introduced continuously to the autoclave over a period of 1.5 hours after which the stirring is continued for. an additional time of 0.5 hour.

The resultant mixture of reaction products is separated into a hydrocarbon layer and a heavier catalyst layer. The used catalyst is returned to while the hydrocarbon layer is fractionally distilled to separate from higher boiling alkylation products the unreacted isobutane and small amounts of hydrogen fluoride which generally from the group consisting of the acids of phosphorus and their anhydrides and esters.

2. An alkylation process which comprises reacting an isoparaflin with an olefin in the presence of a liquid hydrogen fluoride catalyst to which has been added a minor proportion of an acid of phosphorus.-

3. An alkylation process which comprises reacting an isoparaifln with an olefin in the presence of a liquid hydrogen fluoride catalyst to which has been added a minor proportion of a phosphoric acid.

4. A process for synthesizing substantially saturatedhydrocarbons of gasoline boiling range which comprises alkylating an isoparaflinic hydrocarbon with an olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of -liquidhydrogen fluoride and a relatively minor proportion of a substantially non-oxidizing compound soluble in said hydrogen the autoclave for use in another alkylation run dissolve in the hydrocarbon layer. The recovered isobutane is used in another alkylation run while the higher boiling hydrocarbons are washed with water and caustic soda solution, then dried and distilled to separate therefrom a substantially saturated fraction of gasoline boiling range containing a high proportion of branched chain octanes.

From 1,000 volumes (approximately 5'10 parts by weight) of the isobutane-normal butene mixture there is obtained approximately .370 parts by weight of normally liquid parafllnic hydrocarbons containing 90% by volume of 300 F. endpoint aviation gasoline with an octane number of 92.5.

Example II A mixture of 3 molecular proportions of iso-- and 20 parts by weight of glacial acetic acid. Thus 850 parts by weight of the isobutane-normal butene mixture is added continuously over a period of 2 hours after which the hydrocarbon arates the excess of unreacted isobutane from a total of about 400 parts by weight of parafiinic hydrocarbons of gasoline boiling range having an fluoride and selected from the group consisting of the acids of phosphorus and their anhydrides I and esters.

5. A process for synthesizing substantially saturated hydrocarbons of gasoline boiling range which comprises alkylating an isoparaflinic hydrocarbon with an olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion of an anhydride of an acid of phosphorus.

6. A process for synthesizing substantially saturated hydrocarbons of gasoline bofling range which comprises alkylating an isoparaflinic hydrocarbon with an olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion of an ester of an acid of phosphorus.

'7. The process of claim 4 further characterized. in that said substantially non-oxidizing compound is a phosphoric acid.

8,. The process of claim 4 further characterized in that said substantially non-oxidizing compound is an acid of phosphorus.

9. A process for synthesizing substantially saturated hydrocarbons of gasoline boiling range which comprises contacting an isoparaflinic hylayer is separated fromthe catalyst layer. Fracvtional distillation of the hydrocarbon layer sepoctane number of 92. The recovered isobutane and used catalyst are further utilized in' another drocarbon with an olefinic hydrocarbon at a temperature between about -30 and about C. in the presence of acatalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relativelyv minor proportion of a substantially non-oxidizing compound selected from the group consisting of the acids of Phosphorus and their anhydrides and esters.

10. A process for'synthesizing substantially 5a"- urated hydrocarbons of gasoline boiling range which comprises contacting an isoparafllnic hydrocarbon with an olefinic hydrocarbon in the presence of a catalyst-comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion oi. a substantially non-oxidizing compound selected from the group consistingof the acids of phosphorus and their anhydrides and esters and at a temperature between about -30 and about 100 C. under a pressure suflicient to maintain in liquid state a substantial proportion 01 the reacting hydrocarbons and catalyst.

11. A process for synthesizing substantially saturated hydrocarbons of gasoline boiling range which comprises contacting a major molecular proportion of an isoparamnic hydrocarbon with a relatively minor molecular proportion of an olefinic hydrocarbon in the presence of a catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion of a substantially non-oxidizing compound selected from the group consisting or the acids of phosphorus andtheir anhydride; and esters and at a temperature between about -30 and about 100 C. under a pressure suflicient to aas'laoos maintain in liquid state a substantial proportion of the reacting hydrocarbons and catalyst.

12. A process for synthesizing substantially saturated hydrocarbons of gasoline boiling range which comprises contacting at least 2 molecular proportions of an isoparaillnic hydrocarbon with 1 molecular proportion 01' an oleiinic hydrocarbon in the presence of a'catalyst comprising essentially a major proportion of liquid hydrogen fluoride and a relatively minor proportion oi a substantially non-oxidizing compound selected from the group consisting of the acids of phosphorus and their anhydrides .and esters and at a temperature between about 30 and about 100 C. under a pressure sufllcient to maintain in liquid state a substantial proportion of the reacting hydro- 1 carbons and catalyst.

13. The process of claim 12 further characterized in that said substantially non-oxidizina acid is an acid of phosphorus.

CARL B. LINN. 

